PSK Trammune

What is PSK?

PSK is a proteoglycan found in the mushroom Coriolus or Trametes versicolor. The results obtained from a large number of published scientific studies and clinical trials showed that PSK is a powerful immunomodulator capable of stimulating diverse immunological functions.

Depressed Immunity

A depressed immunity can be attributed to a number of causes including advanced age, stress, poor gut barrier function, infection, disease, exposure to carcinogens and treatment with immunosuppressive agents including chemotherapy and radiation therapy.

Effectiveness of immunochemotherapy with PSK, a protein-bound polysaccharide, in colorectal cancer and changes of tumor marker.

Abstract
In the present study, curatively resected patients of colorectal cancer at pTNM stages II and III were selected. Patients receiving postoperative combined PSK, a protein-bound polysaccharide, and fluoropyrimidine therapy (PSK + chemotherapy group) were compared with patients receiving postoperative chemotherapy alone (chemotherapy group) during the same period of study. Three-year disease-free survival rates were evaluated and the postoperative changes of serum type IV collagen level were investigated. The results confirmed a significant improvement of the three-year disease-free survival rate in the PSK + chemotherapy group compared to the chemotherapy group, suggesting that PSK is useful as postoperative prognosis control including relapse prevention for colorectal cancers at pTNM stage II and III. Analysis of the postoperative changes of serum type IV collagen level showed significantly higher levels in the chemotherapy group than in the PSK + chemotherapy group, and this tendency was sustained for 12 months after surgery. This observation is speculated to be caused by inhibition of vascular basement membrane destruction by PSK, leading to inhibition of release of type IV collagen into the blood. These results indicated a possibility that combined PSK and chemotherapy inhibited metastasis, thereby reducing the risk of relapse and leading to improvement of the three-year disease-free survival rate.

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Polysaccharide-K (PSK) in cancer–old story, new possibilities?

Polysaccharide-K (PSK, Krestin) is one of the most commonly used medicinal mushroom extracts with a long history as an additive in cancer therapy in Asia, especially in Japan. PSK has a documented anti-tumor activity both in vitro and in vitro, in various types of cancers, including colorectal, gastric, breast, liver, pancreatic, and lung cancer. Despite PSK having been studied for about 40 years as an immune modulator and biological response modifier, the mechanisms of action by PSK have not yet been clearly and completely elucidated. This review aims to provide an up-to-date account for the effects of PSK in cancer with the hope of thereby providing an increased understanding of the molecular mechanisms of PSK and also its potential as an additive in modern cancer therapy.

Polysaccharide-K (polysaccharide-Kureha; PSK), also known as krestin, is a unique protein-bound polysaccharide, which has been used as a chemoimmunotherapy agent in the treatment of cancer in Asia for over 30 years. PSK and Polysaccharopeptide (PSP) are both protein-bound polysaccharides which are derived from the CM-101 and COV-1 strains of the fungus Coriolus versicolor by Japanese and Chinese researchers, respectively. Both polysaccharide preparations have documented anticancer activity in vitro, in vivo and in human clinical trials, though PSK has been researched longer and has therefore undergone more thorough laboratory, animal and clinical testing. Several randomized clinical trials have demonstrated that PSK has great potential as an adjuvant cancer therapy agent, with positive results seen in the adjuvant treatment of gastric, esophageal, colorectal, breast and lung cancers. These studies have suggested the efficacy of PSK as an immunotherapy or biological response modifier (BRM). BRMs potentially have the ability to improve the “host versus tumor response,” thereby increasing the ability of the host to defend itself from tumor progression. The mechanisms of biological response modification by PSK have yet to be clearly and completely elucidated. Some studies suggest that PSK may act to increase leukocyte activation and response through up-regulation of key cytokines. Indeed, natural killer (NK) and lymphocyte-activated killer (LAK) cell activation has been demonstrated in vivo and in vitro, and recent genetic studies reveal increased expression of key immune cytokines in response to treatment with PSK. An antimetastatic action of PSK has also been demonstrated and is perhaps attributed to its potential to inhibit metalloproteinases and other enzymes involved in metastatic activity. PSK has also been shown to cause differentiation of leukemic cells in vitro, and this effect has been attributed to induction of differentiation cytokines. PSK has further been shown to have antioxidant capacity which may allow it to play a role as a normal tissue chemo- and radio-protector when used in combination with adjuvant or definitive chemotherapy and/or radiotherapy in the treatment of cancer, while it may also enable it to defend the host from oxidative stress. Interestingly, studies have also shown that PSK may actually inhibit carcinogenesis by inhibiting the action of various carcinogens on vulnerable cell lines. This action of PSK may play a role in preventing second primary tumors when an inducing agent, such as tobacco or asbestos, is suspected and may also prevent second malignancies due to the carcinogenic effects of radiotherapy and cytotoxic chemotherapy. Another very important aspect of chemoimmunotherapy, in general is that it may be used on debilitated patients such as those with AIDS and the elderly who might otherwise be denied potentially helpful adjuvant cytotoxic chemotherapy. Further determination of the mechanisms of these anti-cancer, immunostimulating and biological response modifying effects of PSK as well as of other protein-bound polysaccharides is certainly warranted. Indeed, with modern cellular and molecular biology techniques, a better understanding of the specific molecular effects of PSK on tumor cells as well as leukocytes may be determined. Much of the research that has been done on PSK is outlined in this paper and may serve as a foundation toward determining the mechanisms of action of this and other protein-bound polysaccharides in the treatment of cancer. This information may open new doors in the development of novel strategies for the treatment of malignancies using adjuvant immunotherapy in combination with surgery, chemotherapy and/or radiotherapy.

Abstract
PSK, a protein-bound polysaccharide, is widely used in Japan as an immunopotentiating biological response modifier for cancer patients. PSK exerts antitumor activities through stimulation of the host’s immune response; however, few studies have addressed the direct actions of PSK on tumor cells. Recently, it has been found that STAT3 is aberrantly activated in various types of malignancies, and plays a crucial role in tumor cell proliferation and survival. In the present study, STAT3 was constitutively activated in KYSE170 and TE13 esophageal carcinoma cells, and PSK inhibited proliferation and induced apoptosis in these cells in a dose-dependent manner. Based on these findings, the relationship between STAT3 and apoptosis in these cells was investigated. Results showed that PSK inhibited the expression of activated STAT3 and stimulated the expression of pro-apoptotic Bax in a dose-dependent manner, without affecting the expression of anti-apoptotic Bcl-xL and Mcl-1. These results indicate that PSK may induce apoptosis in esophageal carcinoma cells by inhibiting the expression of activated STAT3.

Abstract
Docetaxel, a member of the taxane family, has been shown to induce apoptosis in a variety of cancer cells. However, toxicity at therapeutic doses has precluded the use of docetaxel alone for the management of cancer patients. PSK, a protein-bound polysaccharide, is widely used in Japan as an immunopotentiating biological response modifier for cancer patients. Our previous study showed that PSK induced downregulation of several invasion-related factors, suggesting an interaction of PSK with transcriptional factors. In this study, we showed that PSK dose dependently enhanced apoptosis induced by 1 nM of docetaxel in a human pancreatic cancer cell line NOR-P1. Furthermore, PSK inhibited docetaxel-induced nuclear factor kappa B (NF-kappaB) activation. Moreover, the expression of cellular inhibitor of apoptosis protein (cIAP-1), which is transcriptionally regulated by NF-kappaB and functions as an antiapoptotic molecule through interrupting the caspase pathway, was also inhibited by treatment with PSK plus docetaxel. As a result, PSK enhanced the docetaxel-induced caspase-3 activation. In addition, treatment by transfection of NF-kappaB decoy oligodeoxynucleotides (ODNs), but not scramble ones, inhibited the expression of cIAP-1 in NOR-P1 cells and induced a significant increase in docetaxel-induced apoptosis. Our data indicate that PSK suppresses the docetaxel-induced NF-kappaB activation pathway. Combination of PSK with a low dose of docetaxel may be a new therapeutic strategy to treat patients with pancreatic cancer.

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Medicinal mushrooms as a source of antitumor and immunomodulating polysaccharides.

Abstract
The number of mushrooms on Earth is estimated at 140,000, yet maybe only 10% (approximately 14,000 named species) are known. Mushrooms comprise a vast and yet largely untapped source of powerful new pharmaceutical products. In particular, and most importantly for modern medicine, they represent an unlimited source of polysaccharides with antitumor and immunostimulating properties. Many, if not all, Basidiomycetes mushrooms contain biologically active polysaccharides in fruit bodies, cultured mycelium, culture broth. Data on mushroom polysaccharides have been collected from 651 species and 7 infraspecific taxa from 182 genera of higher Hetero- and Homobasidiomycetes. These polysaccharides are of different chemical composition, with most belonging to the group of beta-glucans; these have beta-(1–>3) linkages in the main chain of the glucan and additional beta-(1–>6) branch points that are needed for their antitumor action. High molecular weight glucans appear to be more effective than those of low molecular weight. Chemical modification is often carried out to improve the antitumor activity of polysaccharides and their clinical qualities (mostly water solubility). The main procedures used for chemical improvement are: Smith degradation (oxydo-reducto-hydrolysis), formolysis, and carboxymethylation. Most of the clinical evidence for antitumor activity comes from the commercial polysaccharides lentinan, PSK (krestin), and schizophyllan, but polysaccharides of some other promising medicinal mushroom species also show good results. Their activity is especially beneficial in clinics when used in conjunction with chemotherapy. Mushroom polysaccharides prevent oncogenesis, show direct antitumor activity against various allogeneic and syngeneic tumors, and prevent tumor metastasis. Polysaccharides from mushrooms do not attack cancer cells directly, but produce their antitumor effects by activating different immune responses in the host. The antitumor action of polysaccharides requires an intact T-cell component; their activity is mediated through a thymus-dependent immune mechanism. Practical application is dependent not only on biological properties, but also on biotechnological availability. The present review analyzes the pecularities of polysaccharides derived from fruiting bodies and cultured mycelium (the two main methods of biotechnological production today) in selected examples of medicinal mushrooms.

The mouse macrophage-like cell line, J774.1, spontaneously released
differentiation-inducing factor(s). When these cells were treated
with a protein-bound polysaccharide, PSK, significantly higher
amounts of differentiation-inducing activity were accumulated in the
culture supernatant. PSK directly stimulated human myelogenous
leukemic cell differentiation induced by J774.1 conditioned medium or
by tumor necrosis factor. Among four subfractions of PSK, only the
highest molecular weight fraction (MW greater than 200 kD) exerted
such a stimulating effect.

*****JAPANESE JOURNAL OF CANCER RESEARCH*****

(REFERENCE 2 OF 41)

Ebina T Murata K
Antitumor effect of PSK at a distant site: tumor-specific immunity
and combination with other chemotherapeutic agents.

In: Jpn J Cancer Res (1992 Jul) 83(7):775-82

The antitumor effect of PSK, a Coriolus preparation, was analyzed
with the double grafted tumor system in which BALB/c mice received
intradermal inoculations of syngeneic Meth-A fibrosarcoma in the
right (primary tumor, 10(6) cells) and left (distant tumor, 2 x 10(5)
cells) flanks. Intratumoral administration of PSK significantly
inhibited the growth of not only the right but also the left tumor.
PSK also inhibited the growth of a methylcholanthrene-induced
fibrosarcoma BAMC-1, and a methylurethane-induced adenocarcinoma
Colon 26 in the double grafted tumor system of syngeneic BALB/c mice.
However, when the left distant tumor was different from the right
Meth-A tumor, the intratumoral administration of PSK in the right
tumor was unable to inhibit the growth of the left BAMC-1 or RL male-
1 tumor. The PSK-induced immunity, therefore, is tumor-specific and T
lymphocytes may play an important role in antitumor memory function.
The enhancement of concomitant immunity by PSK treatment was
completely impaired by previous intravenous administration of an
alkylating agent, cyclophosphamide (CY). The enhancement of
sinecomitant immunity by PSK treatment was also impaired by previous
CY intravenous administration. The antitumor effect of PSK was
suppressed by previous intravenous administration of another
alkylating agent, ACNU. It is possible that alkylating agents
suppress the function of effector T cells and granulocytes which are
very important for the antitumor immune cascade reaction due to PSK
treatment. On the other hand, the antitumor effect of PSK was
enhanced by previous intravenous administration of an anti-
metabolite, 5-fluorouracil.

The protein-bound polysaccharide PSK was tested for the ability to
induce in vitro autologous tumor killing (ATK) activity in human
cancer patients. Peripheral blood lymphocytes (PBL) and tumor-
infiltrating lymphocytes (TIL) demonstrated various levels of
cytotoxicity against autologous, freshly isolated tumor cells. When
PBL and TIL were cultured overnight with PSK, ATK activity was
induced in previously non-reactive cases and augmented in previously
reactive samples. The PSK effect was observed with PSK concentrations
of 10-100 micrograms/ml that could be obtained in the blood of cancer
patients who received standard oral administration of PSK. The
manifestation of PSK-induced ATK required active cell metabolism and
RNA and protein syntheses, but not DNA synthesis of lymphocytes. PSK-
induced enhancement of ATK was not abrogated by monoclonal antibodies
(mAb) directed against interferon (IFN) alpha or IFN gamma. In
addition, mAb that neutralized interleukin-2 (IL-2) or mAb reactive
with alpha-chain or beta-chain of IL-2 receptors (IL-2R) had no
effect on PSK-induced ATK activity. Supernatants from PSK-stimulated
lymphocyte cultures did not induce ATK. Cell fractionation
experiments revealed that CD3-CD16+ large granular lymphocytes (LGL)
and/or CD3+CD16- T lymphocytes were responsible for both spontaneous
and PSK-induced ATK. PSK-activated LGL, but not T lymphocytes
expressed lysis of fresh allogeneic tumor cells. These results
indicate that PSK activates PBL and TIL to exhibit ATK independently
of IL-2/IL-2R systems.

(REFERENCE 4 OF 41)

Ebina T Kohya H Ishikawa K
Antitumor effect of PSK: role of regional lymph nodes and enhancement
of concomitant and sinecomitant immunity in the mouse.

In: Jpn J Cancer Res (1989 Feb) 80(2):158-66

PSK, a Coriolus preparation, inhibited the growth of not only the
right but also the left, non-treated tumor in a double grafted tumor
system. In order to examine the role of lymph nodes and the spleen in
the antitumor activity of PSK, regional (axillary and inguinal) lymph
nodes and spleen were resected. Since in resected mice the antitumor
activity of PSK against the right and left tumors was weakened, the
regional lymph nodes and the spleen probably have a very important
role in the antimetastatic effect of intratumoral administration of
PSK. TIL (tumor-infiltrating lymphocytes) obtained from left and
right side tumors treated with PSK were examined by Winn assay for
their antitumor activity against Meth-A sarcoma in BALB/c mice. TIL
from both sides clearly inhibited the growth of admixed Meth-A cells,
but control TIL did not. A primary growth of Meth-A sarcoma
inoculated into the right flank resulted in the generation of
concomitant immunity to the growth of a second graft of the same
tumor cells in the left flank. A significant inhibitory effect on the
proliferation of the tumor cells inoculated secondarily was shown in
mice bearing a primary right tumor that had previously been
inoculated with PSK 3 times. After surgical excision of the primary
tumor on day 6, daily oral administration of PSK significantly
inhibited the growth of the secondary tumor inoculated on day 21,
that is, PSK treatment also enhanced sinecomitant immunity. These
observations suggest that presurgical intratumoral injection and
postoperative oral administration of PSK are highly effective in
eradicating metastatic tumors.

(REFERENCE 5 OF 41)

Kikuchi Y Kizawa I Oomori K Iwano I Kita T Kato K
Effects of PSK on interleukin-2 production by peripheral lymphocytes
of patients with advanced ovarian carcinoma during chemotherapy.

In: Jpn J Cancer Res (1988 Jan) 79(1):125-30

The effects of PSK on OKT 4/OKT 8 cell ratio, interleukin-2 (IL-2)
production and expression of IL-2 receptor were examined in
peripheral blood lymphocytes (PBL) from patients with advanced
ovarian cancer during the course of chemotherapy. Preoperative levels
of OKT 4/OKT 8 cell ratio and IL-2 production in PBL from patients
with advanced ovarian cancer were significantly lower than those in
cases of benign ovarian tumor. However, the expression of IL-2
receptor did not show any significant difference between ovarian
cancer and benign ovarian tumor patients. When a combination
chemotherapy of cisplatin, adriamycin and cyclophosphamide was given,
the OKT 4/OKT 8 cell ratio was significantly increased with a
significant decrease of the absolute number of the OKT 8 cell subset,
while the expression of IL-2 receptor and the absolute number of the
OKT 4 cell subset remained unchanged. In contrast, the IL-2
production was markedly depressed after the first course of
chemotherapy. When PSK was combined with combination chemotherapy,
the degree of inhibition of IL-2 production was reduced (though the
effect was not statistically significant). If treatment with PSK was
initiated after completion of combination chemotherapy, in addition
to a significant elevation of OKT 4/OKT 8 cell ratio the depressed IL-
2 production was restored to benign control levels. On the other
hand, the expression of IL-2 receptor remained unchanged even if PSK
was given after completion of chemotherapy.

In Japan the standard adjuvant treatment after resection of gastric
cancer is intravenous mitomycin plus oral fluorouracil. We have
assessed the efficacy of protein-bound polysaccharide (PSK) in
addition to standard chemotherapy in patients who had undergone
curative gastrectomy at 46 institutions in central Japan. 262
patients were randomly assigned standard treatment alone or with PSK.
The minimum follow-up time was 5 years (range 5-7 years). PSK
improved both the 5-year disease-free rate (70.7 vs 59.4% in standard
treatment group, p = 0.047) and 5-year survival (73.0 vs 60.0%, p =
0.044). The two regimens had only slight toxic effects, consisting of
nausea, leucopenia, and liver function impairment, and there were no
significant differences between the groups. The treatments were
clinically well tolerated and compliance was good. Addition of PSK to
adjuvant chemotherapy with mitomycin and fluorouracil is beneficial
as treatment after curative gastrectomy.

*****ANTICANCER RESEARCH*****

(REFERENCE 9 OF 41)

Sakagami H Kawazoe Y
NOVEL ELUCIDATION OF THE MECHANISM OF INDUCTION OF VARIOUS
IMMUNOPOTENTIATING ACTIVITIES BY A PROTEIN-BOUND POLYSACCHARIDE, PSK
(MEETING ABSTRACT)

In: Anticancer Res (1990) 10(5B):1472

A protein-bound polysaccharide, PSK, extracted from the mycelium of
Coriolus versicolor (Fr) Quel, has been recognized for its host-
mediated antitumor and antimicrobial activity in mice. Since PSK is a
plant extract, it could contain several active ingredients. However,
intact PSK has been used in almost all experiments. We recently
reported that, among the four subfractions separated by the mol wt,
only the highest mol wt fraction, F4 (mol wt greater than 200 kD),
induced significant antimicrobial activity in mice. PSK and F4
stimulated the differentiation of human myelogenous leukemia cell
lines toward monocyte/macrophages, induced by various cytokines such
as tumor necrosis factor (TNF) and interferon-r (IFN-r). Binding
studies with 125I-TNF or 125I-IFN-r suggest that the stimulating
effect of the active PSK subfractions might be associated with
inhibition of the downregulation of receptor binding of these
cytokines. PSK also stimulated the iodination (incorporation of
radioactive iodine into an acid-insoluble fraction) of human
peripheral blood polymorphonuclear cells (PMN), and the NBT-reducing
activity of mouse peritoneal resident macrophages. Among the
subfractions of PSK, whether separated by mol wt or by isoelectric
point precipitation, the highest mol wt fraction F4, and the fraction
precipitated at pH 4.0-4.5 (Fr 4), stimulated macrophage NBT-reducing
activity and PMN iodination most. In contrast, natural and chemically
modified glucans had little or no stimulating activity. We recently
found that iv administration of PSK significantly stimulated OK-432-
elicited endogenous cytotoxic factor (possibly TNF) production in
mouse serum. The data suggest that (1) immunopotentiation activity of
PSK might be ascribed, at least in part, to the stimulation or
production of various cytokines, and (2) PSK might have some unique
component(s) which directly stimulate the macrophage/PMN function.
Therefore, the necessity of an advanced structure-activity
relationship is indicated and further studies of this need are
underway in our laboratory.

We have previously shown that oral administration of PSK not only
exerts antitumor activity, but also restores immune response in tumor-
bearing mice. In order to analyze the immunomodulative effect of PSK,
we investigated the effects of oral PSK on the intestinal immune
systems in ICR mice bearing sarcoma 180. Oral administration of PSK
increased the number of Peyer’s patches that developed relatively
well, and led to recovered mitogenic response of lymphocytes from gut-
associated lymphatic tissue and responsiveness to oral
preimmunization with SRBC in tumor-bearing mice. These results
suggest that PSK modulates the immunity in intestinal tract of tumor-
bearing mice.

From 1976 to 1985, 185 patients with non-small cell lung cancer at
stages I-III were treated with definitive radiotherapy in Gunma
University Hospital. As a result of analyzing the long-term survivors
treated with radiotherapy, suitable conditions of the patients for
radical radiotherapy were as follows; 1) stage I or II, and some
stage III, 2) as regards the histologic type epidermoid carcinoma or
well-differentiated adenocarcinoma, 3) as regards the primary sites,
the upper lobe and the superior segment of the lower lobe, 4) the
optimum dose was 60-70Gy, 5) the size of the radiation fields given >
40Gy was 100 cm2 or less, and 6) the host condition was satisfactory
(BRM combined use). In particular, as a result of administering PSK
as adjuvant treatment to patients with epidermoid carcinoma of the
lung showing satisfactory tumour shrinkage after radiotherapy, the
five year survival rate of the patients with stages I or II disease,
as well as stage III was 39% and 22% respectively, compared with the
non-administered group’s 16% and 5%. These differences are
statistically significant. Although an improvement in the results of
treatment with the combined use of appropriate BRMs is anticipated in
the future, when clinical trials for combined BRM and radiotherapy
are planned, the subjects should be patients with satisfactory tumour
regression after radiotherapy.

A total of 20 mg of 7,12-dimethylbenz[a]anthracene (DMBA) was
administered orally to 41 female Sprague-Dawley (SD) rats (control
group), and 60 mg/kg of Krestin (PSK) were orally administered daily
to 38 rats (PSK group) after DMBA administration. The average
development period (9.6 weeks) of DMBA-induced tumors in the PSK
group was significantly longer (P < 0.02) than that (7.9 weeks) in
the control group. Average estrogen receptor (ER) levels of
established tumors were almost the same between these two groups.
However, the chemotherapeutic effect of tamoxifen (TAM) was
significantly enhanced by PSK pretreatment.

A protein-bound polysaccharide, PSK, extracted from the mycelium of
Coriolus versicolor (Fr.) Quel, has been recognized for its host-
mediated induction of antitumor and antimicrobial activities in mice.
Intravenous administration of PSK, in association with OK-432
(Picibanil), transiently induced endogenous production of a cytotoxic
factor (CF) (possibly tumor necrosis factor, TNF) in normal mice. The
ability to produce CF depended greatly on both dose and interval
between administration of the PSK and OK-432. Although PSK has been
reported to contain several active ingredients, unfractionated PSK
has been used in almost all experiments performed so far. We recently
reported that, of the four subfractions separated by successive
filtration through membrane filters, only the highest molecular
weight fraction F4 (MW greater than 200 kD) induced significant
antimicrobial activity in mice. PSK stimulated the NBT-reducing
activity of mouse peritoneal macrophages and the iodination
(incorporation of radioactive iodine into an acid-insoluble fraction)
of human peripheral blood polymorphonuclear cells (PMN). Among the
subfractions of PSK, the highest molecular weight fraction F4, and
the fraction precipitated at pH 4.0-4.5 (Fr. 4), stimulated
macrophage NBT-reducing activity and PMN iodination most. In
contrast, natural and chemically modified glucans had little or no
stimulating activity. PSK, F4 or Fr. 4 additively or synergistically
stimulated TNF-induced cytotoxicity against L-929 cells,
differentiation of human myelogenous leukemia cell lines toward
monocytes/macrophages, and iodination of human peripheral blood PMN.
The active PSK subfractions significantly reduced the down regulation
of specific 125I-TNF or 125I-IFN-gamma binding to cellular receptors.
These data suggest that (i) immunopotentiation activity of PSK might
be ascribed, at least in part, to stimulation of cytokine action and
production, and (ii) PSK might have some unique structural features.

The present study was designed to assess the effects of the protein-
bound polysaccharide PSK on the immunological status of patients with
gastrointestinal cancer. Twenty-nine gastric and 18 colorectal cancer
patients were randomly assigned to either the control or PSK group.
Patients in the PSK group were given 3.0 g of PSK orally before
surgery, either daily or every other day. Patients in the control
group received no PSK. The data of peripheral blood lymphocytes (PBL)
were compared before and after administration of PSK, and those of
the regional node lymphocytes (RNL) were compared between the control
and the PSK group. The results indicate that the effects of PSK were
significantly influenced by the duration of administration, but not
by the frequency of administration. In the patients belonging to the
short term PSK group (administration less than 14 days), the response
of the PBL to PSK and Con A become significantly stronger compared to
before the administration of PSK, whereas the cytotoxicity against
K562 and KATO-3, and the proportion of CD16+ cells increased
significantly in those patients belonging to the long term PSK group
(greater than or equal to 14 days). In addition, the proportion of
CD9 + 11b + suppressor T cells decreased in the RNL of the short term
PSK group, whereas the proportion of CD4 + Leu8 – helper T cells in
the RNL increased in the long term PSK group. These results suggest
that the oral administration of PSK leads to the suppression of
suppressor cells in the RNL.(ABSTRACT TRUNCATED AT 250 WORDS)

BACKGROUND. A randomized adjuvant trial was conducted from October
1982 to January 1985 to evaluate the addition of tamoxifen (TAM) to
combination chemotherapy with perioperative mitomycin C (MMC) and
ftorafur (FT) for patients with estrogen receptor (ER)-positive
tumors and the addition of PSK, a biologic response modifier, to
MMC+FT chemotherapy for patients with ER-negative tumors in operable
Stage IIA, IIB, and IIIA cancer. The doses used were 20 mg of oral
TAM daily, 600 mg of oral FT daily, and 3 g of oral PSK daily for 2
years. Intravenous MMC (13 mg/m2) was given on the day of operation.
METHODS. A total of 967 patients were entered and randomized by
stratification based on ER status and staging (1978 International
Union Against Cancer [UICC] criteria at the time of trial execution).
Of 967 patients, 914 (94.5%) were evaluable. At 5-year follow-up,
significant prolonged overall survival (OS) and relapse-free survival
(RFS) times were seen with the addition of TAM in patients with ER-
positive and Stage IIIA T3N0 cancer (1987 UICC-American Joint
Committee on Cancer [AJCC] criteria); however, no significant
survival benefit from TAM was seen in patients with ER-positive and
Stage IIA T2N1 cancer. There was no significant difference between
regimens, with or without PSK, in patients with ER-negative disease.
RESULTS. Results of subset analyses suggested a benefit from TAM in
postmenopausal patients with ER-positive and Stage IIA T2N1 cancer
and a benefit from PSK in patients with node-negative, ER-negative,
and Stage IIA T2N1 cancer. CONCLUSIONS. The 5-year results of the
current trial showed a survival advantage by the addition of TAM to
chemotherapy in patients with ER-positive and Stage IIIA T3N0 cancer.

*****CANCER EPIDEMIOLOGY, BIOMARKERS AND PREVENTION*****

(REFERENCE 16 OF 41)

Kobayashi H Matsunaga K Fujii M
PSK as a chemopreventive agent.

In: Cancer Epidemiol Biomarkers Prev (1993 May-Jun) 2(3):271-6

PSK, a protein-bound polysaccharide preparation obtained from
cultured mycelia of the CM-101 strain of Coriolus versicolor
belonging to basidiomycetes, is a biological response modifier
capable of exhibiting diverse biological activities. This agent has
been used clinically for the treatment of postoperative cancer
patients in Japan by oral use. In this paper, chemopreventive aspects
of PSK were reviewed. Oral administration of PSK reduced the
incidence of tumor and/or prolonged the survival period in the
following chemical carcinogen-induced, radiation-induced, and
spontaneously developed animal cancer models: rat gastrointestinal
cancer induced by 1,2-dimethylhydrazine; rat hepatoma by 3′-methyl-
dimethylaminobenzene; mouse thymic lymphoma by whole-body
irradiation; mouse spontaneous mammary tumor; and so on. PSK did not
interact and/or inhibit drug-metabolizing enzymes and had no effect
on the Ames test. On the other hand, this agent scavenged active
oxygen through the induction of manganese superoxide dismutase,
prevented the increase in frequency of anticancer agent-induced
sister chromatid exchange, and suppressed fetal deformation induced
by transplacental injection of teratogen, suggesting an effect on the
initiation or promotion process of carcinogenesis. Also, PSK
regulated cytokine production and enhanced the antitumor activity of
effector cells such as killer T-cells and natural killer cells,
suggesting an effect on the growth process after the development of
malignant cells. Thus, this agent seems to act at multiple steps
during carcinogenesis rather than a particular step. The main
mechanism may be an antiteratogenic effect attributed to radical
trapping, preventive effects against chromosome injury, and
immunomodulative effects attributed to the modulation of cytokine
production and effector cell function.(ABSTRACT TRUNCATED AT 250
WORDS)

To examine the clinical efficacy and the mechanism of action of
polysaccharide K (PSK), a protein-bound polysaccharide extracted from
a Basidiomycetes fungus, a randomized double-blind trial was
performed by administering PSK to 56 patients and a placebo to
another group of 55 patients after surgical operations on their
colorectal cancers. The rate of patients in remission (or disease-
free) was significantly higher in the PSK group than in the placebo
group; the difference between both groups was statistically
significant at P less than 0.05 by the log-rank test. The survival
rate of patients was also significantly (P less than 0.05) higher in
the PSK group than in the control group. The most significant
laboratory finding was that polymorphonuclear leukocytes from PSK-
treated patients showed remarkable enhancement in their activities,
such as random and/or chemotactic locomotion, and phagocytic
activity, when compared with those in the control group. In
conclusion, PSK was useful as a maintenance therapy for patients
after their curative surgical operations for colorectal cancer. The
beneficial effects were probably due to the activation of leukocyte
functions as one of the many biological-response-modifying
(activities induced by PSK).

A polysaccharide preparation isolated from Coriolus versicolor (Fr.)
Quel. of Basidiomycetes (PSK) predominantly consists of glucan and
approximately 25% tightly bound protein. PSK was effective against
various allogeneic and syngeneic animal tumors and has been given
orally to cancer patients. Various suppressed or enhanced immune
responses of tumor-bearing animals were restored to normal levels by
the administration of PSK in the tumor models tested. The killer T
cell activity was augmented in tumor-bearing mice by intraperitoneal
or oral administration of PSK, and there was correlation between the
PSK associated antitumor effect and the killer T cell activity. It
was found that PSK competed with immunosuppressive substances
isolated from tumor-bearing mice and that the intestinal immune
system appeared to be modulated by oral administration of PSK. After
oral administration of 14C- or 35S-labeled PSK to normal rats, it was
found that small or large molecular substances appeared in the serum
depending on the time elapsed after administration, an indication
that large molecular size products were from the digestive tract.

A randomized, controlled trial of adjuvant immunochemotherapy with
PSK (Kureha Chemical Industry Co., Tokyo, Japan) in curatively
resected colorectal cancer was studied in 35 institutions in the
Kanagawa prefecture. From March 1985 to February 1987, 462 patients
were registered. Four hundred forty-eight of those patients (97.0
percent) satisfied the eligibility criteria. The control group
received mitomycin C intravenously on the day of and the day after
surgery, followed by oral 5-fluorouracil (5-FU) administration for
over six months. The PSK group received PSK orally for over three
years, in addition to mitomycin C and 5-FU as in the control group.
At the end of February 1990, the median follow-up time for this study
was four years (range, three to five years). The disease-free
survival curve and the survival curve of the PSK group were better
than those of the control group, and differences between the two
groups were statistically significant (disease-free survival, P =
0.013; survival, P = 0.013). These results indicate that adjuvant
immunochemotherapy with PSK was beneficial for curatively resected
colorectal cancer.

Long-term administration of PSK was given to 35 patients with cancer
of the digestive organs and breast during the so-called maintenance
period or the follow-up period. The mean duration of administration
was about 9 mo. Delayed skin tests (purified protein derivative,
candida) and id phytohemagglutinin tests tended to be initially
enhanced, slightly depressed after several mo, and then restored
about 3 mo later, in spite of continuous administration. The
peripheral lymphocyte counts were also increased after a decrease.
Serum IgG, IgA, and IgM were less changed, but IgM and IgG were
slightly increased, but only in the curatively resected cases. No
side effect in the liver, bone marrow, or other organs was seen.
These results indicate that PSK is useful as an immunostimulant in
cancer therapy. Relatively short periods of alternation of PSK with
some other stimulant is assumed to be better than continuous
administration of PSK alone. (Author abstract) (7 Refs)

The mode of antitumor action of the so-called immunopotentiators has
been explained as restoration of the impaired immune response through
cellular immunity. Since most of the preparations available are of
bacterial or plant origin, it is possible that they can activate the
complement system mainly through its alternative pathway. The purpose
of the present investigation is to demonstrate the effect of a
streptococcal preparation Picibanil (OK-432), a protein
polysaccharide from mycelia of Coriolus versicolor Krestin (PSK), and
an aminothiazole derivative Levamisole on human serum complement in
vivo. Aged patients without malignancy, who had a decreased immune
response, as detected by purified protein derivative and
phytohemagglutinin skin tests received sc injection of OK-432 0.l
mg/day, po PSK 3 g/day or po Levamisole 150 mg/day on three
consecutive days of each wk. The classical complement pathway was
determined by the lysis of sensitized sheep RBC [50% hemolytic unit
for complement hemolysis, (CHO-50)] and the alternative pathway by
the lysis of unsensitized rabbit RBC [50% hemolytic unit for
alternative complement hemolysis, (ACH-50)]. The complement
components were measured by the single radial immunodiffusion method.
It was found that the administration of OK-432, PSK, or Levamisole
resulted in the elevation of serum CH50 and ACH50. Complement
components were affected by the use of the preparations, while no
specific tendency could be demonstrated, except for increased C3
level when OK-432 was given. Oral administration of PSK showed the
conversion of C3 from beta 1C to beta 1A mobility, determined by
crossed immunoelectrophoresis. Evidence that immunopotentiators
increase the serum complement level in man leads to the conclusion
that these drugs might have an additional function in potentiating
the host-mediated immune response against malignant tumor via the
complement system. (Author abstract) (22 Refs)

In a randomized controlled study of chemotherapy (CDDP 100 mg/m2 day
1, VDS 3 mg/m2 day 1, 8, 15) vs. immuno-chemotherapy combined with
PSK 3 g/day for adenocarcinoma of the lung (stage III, IV, p. s. 0,
1, 2), response rate for 169 cases with completed extramural review
was 14.2%. As for the response rates for 138 complete cases, the
chemotherapy group showed 17.9%, and the immuno-chemotherapy group
was 16.9%. MST were 330 days and 331 days, respectively. In stage III
cases, the response rates were 11.1% in the chemotherapy group and
37.5% in the immuno-chemotherapy group (p = 0.046). MST were 457 days
(65.3 weeks) and 576 days (82.3 weeks), respectively. In terms of
survival curve, it was suggested that the immuno-chemotherapy group
was superior to the chemotherapy group (logrank test p = 0.075), but
in stage IV cases, there was nothing outstanding in the
immunochemotherapy group.

We examined the effect of PSK on involution of the thymus in tumor-
bearing mice. The weight and cell number of the thymus decreased and
the size distribution (scatter profile) of thymus cells was changed
in X5563-bearing C3H/He mice. Also in these mice, 3H-thymidine
incorporation into the thymus was reduced compared with that in
control mice, as evaluated not only by per organ but also by per 1 mg
of thymus tissue. Such an involution was also observed in tumor-free
mice injected with immunosuppressive substance, which had been
obtained from ascites of X5563-bearing mice and revealed suppressive
activity against lymphocyte proliferation. PSK administration
prevented such modulation in the thymus of tumor-bearing mice and
immunosuppressive substance-injected tumor-free mice. In other words,
it is considered that the various changes in the thymus demonstrated
in tumor-bearing mice may be attributable to the suppression of cell
proliferation in the thymus, that such suppression is caused at least
partly by an immunosuppressive substance which possesses inhibitory
activity against lymphocyte proliferation, and that PSK has an
antagonistic activity against such a substance so as to restore the
function of the thymus in tumor-bearing hosts.

The ability of protein-bound polysaccharide (PSK) to block the
suppressive activity of soluble suppressor factor (SSF) was
investigated. The suppressive activity of SSF derived from U-937
cells on phytohemagglutinin (PHA)-induced lymphocyte proliferative
(LP) response was significantly reduced in the presence of PSK. The
release of SSF was not inhibited by the treatment of U-937 cells with
PSK. The suppressive activity of SSF on LP response to PHA was
significantly decreased by the pretreatment of responder lymphocytes
with PSK. Studies to determine lymphocyte receptor activity were
performed. PSK competed with wheat germ agglutinin (WGA) which
recognized the same receptor as SSF on the surface of the lymphocyte.
Neither PSK nor serum competed with anti-CD4 monoclonal antibody.
Thus, PSK may inhibit SSF-mediated suppression by competing for
specific binding sites on the surface of responder lymphocytes.

The fate of 14C-labelled PSK in the body was investigated. Although
only substances with low mol. wt were observed in blood shortly after
the administration, with time, substances with high mol. wt appeared,
suggesting absorption of PSK in its original form from the digestive
tract. 14C-labelled PSK was distributed in bone marrow, salivary
gland, brain liver, spleen, pancreas and tumor. Approximately 70% of
14C-labelled PSK was excreted by expiratory air after 24 h and
approximately 15-20% in urine after 72 h. Only a small amount of 14C-
labelled PSK was transferred into lymph and bile. The present study
on the in vivo behavior of PSK provides an important basis for
further analysis of its pharmacological actions.

We have studied the effects of oral administration of a biological
response modifier (BRM), PSK, on hepatic lymphocytes. Many PSK
positive cells were observed in the liver by anti-PSK antibody
staining. Flow cytometric analysis revealed an increase in the number
of OX8 (CD8) positive cells in the non-parenchymal nonadherent liver
cells (NPNALCs) which were isolated from the liver enzymatically
digested by perfusion with collagenase. NPNALCs were fractionated by
discontinuous density gradient centrifugation, and the number and
cytotoxic activity of these cells were examined in each fraction.
Although the yield of lymphocytes in each fraction was not
significantly increased by the oral administration of PSK, the
natural killer (NK) activity was markedly enhanced in low density
fractions. The present findings suggest that oral administration of
PSK is effective for prevention of liver metastasis through the
augmentation of organ-associated NK activity.

Protein-bound polysaccharide, PSK, is a biological response modifier
and influences various immunological functions in vivo, including
those of T-cells. However, PSK has not been proved to stimulate
proliferation of T-cells in vitro in contrast to various lines of
evidence that indicate the proliferation of B-cells in vitro. PSK
enhanced the proliferation of spleen cells in C3H/He and nude mice in
vitro. In this study such proliferating cells were detected by
monoclonal antibody to bromodeoxyuridine (BrdU) incorporated into
DNA, and their subsets were determined by flowcytometry with
monoclonal antibody to Thy1 as a cell surface marker of T-cells. When
spleen cells from C3H/He mice were cultured with PSK for 3 days, the
percentage of BrdU positive cells increased, and about 67% of BrdU
positive cells were Thy1.2 positive. In addition, PSK also had the
activity to enhance the proliferation in a T-cell-enriched fraction
from spleen cells by nylon fiber columns as well as that in original
spleen cells. These results suggest that PSK enhances the
proliferation of T-cells as well as B-cells.

*****JOURNAL OF CLINICAL AND LABORATORY IMMUNOLOGY*****

(REFERENCE 29 OF 41)

Oguchi Y Morita I Fujii T Matsunaga K Yoshikumi C Kawai Y Tsuru S
Nomoto K
Involution of the thymus in tumor-bearing mice and its restoration by
PSK. II. Mechanism of the involution and its restoration.

In: J Clin Lab Immunol (1987 Oct) 24(2):93-9

In C3H/He mice, the weight and cell number of the thymus were reduced
and the size distribution (scatter profile measured by flow
cytometer) of the thymus cells was changed 1 week after subcutaneous
inoculation of X5563 plasmacytoma. This involution and change were
prevented by intraperitoneal or oral administration of PSK. We
examined the mechanism of this involution and change in thymus and
the effect of PSK on them. In X5563-bearing C3H/He mice, 3H-thymidine
incorporation into the thymus was reduced compared with that in
control mice, as evaluated not only per organ but also per 1 mg of
thymus tissue. Such reduction was inhibited by PSK. The substance (IS
substance) which possessed a suppressive activity against mitogen
induced lymphocyte proliferation, was partially purified from the
ascites of X5563-bearing mice by the combination of ammonium sulfate
precipitation and Sephacryl S-200 chromatography. IS substance was
demonstrated to suppress the antibody response and delayed type foot-
pad response against sheep red blood cells in mice. The reduction of
weight and cell number and the change of scatter profile in thymus
were caused by injection of this substance even in tumor-free mice.
The restorative effects of PSK were observed also in IS substance
injected mice. These results suggested that the various changes in
the thymus observed in tumor-bearing mice might be attributable to
the suppression of cell proliferation in the thymus, that such
suppression was caused at least partly by an immunosuppressive
substance which possessed inhibitory activity against lymphocyte
proliferation, and that PSK had an antagonistic activity against such
a substance so as to restore the function of the thymus in tumor-
bearing hosts.

Our previous studies have indicated that the protein-bound
polysaccharide Kreha (PSK) enhances the cytotoxic activity of
peripheral blood lymphocytes (PBL) against the T24 human urinary
bladder tumor cell line in patients with bladder tumor. Since PSK
consists of a mixture of various kinds of protein-bound
polysaccharides, the present study was designed to examine which
subfractions of PSK mediated the enhancement of cytotoxicity. When
PSK was separated according to size, treatment of PBL with the 50
kilodalton (kd) or less fraction killed T24 cells more efficiently
than unfractionated PSK-treated PBL. The higher molecular weight
fractions did not enhance killing above the control level. PSK was
fractionated on a diethylaminoethyl (DEAE)-cellulose column to obtain
a protein rich fraction that absorbed onto the column and a
polysaccharide rich fraction that did not. PBL treated with the
polysaccharide rich fraction were able to kill T24 cells more
effectively than unfractionated PSK-treated PBL. The protein rich
fraction had no effect on the killing. Further fractionation of the
polysaccharide rich fraction was performed by differential
precipitation with ammonium sulfate. PBL treated with the
precipitated fraction at 70-80% saturation (PSK Fraction D) enhanced
cytotoxicity equal to that of the polysaccharide rich fraction.
Treatment of PBL with the other fractions did not augment the
cytotoxicity. These enhancement by PSK fractions were observed in
healthy donors and also in patients with bladder tumor. An increase
of the proliferative response of PBL to PSK Fraction D as well as
unfractionated PSK was observed. Treatment of PBL with PSK Fraction D
had no effect on the proportion of PBL binding to T24 cells, thus
suggesting a post-binding effect. The structure of PSK Fraction D as
inferred from the results of methylation analysis was mainly an alpha-
glucan. These results demonstrate that PSK mediated enhancement of
cytotoxicity and proliferation of PBL may be largely due to an alpha-
glucan of less than 50 kd.

The effects of Krestin (PSK) on the generation of lymphokine-
activated killer (LAK) cells were examined in tumor-bearing mice.
BALB/c mice were inoculated subcutaneously with methylcholanthrene-
induced fibrosarcoma (Meth A) cells, and PSK was administered
intraperitoneally every other day. The reduced LAK activity in tumor-
bearing mice was restored by the administration of PSK. Since
involvement of the humoral immunosuppressive factor in the impairment
of LAK activity has been suggested, the effect of PSK on the impaired
LAK activity in the presence of an immunosuppressive factor isolated
from the ascites of X5563 (plasmacytoma)-inoculated mice was
examined. The activity reduced by the immunosuppressive factor in an
in vitro induction of LAK was restored by incubation with PSK. The
antimetastatic effect of IL-2 was also augmented by its combined use
with PSK. The data provide a rational basis for using PSK in
combination with recombinant IL-2 in cancer immunotherapy.

Effects of polysaccharide-Kureha (PSK) were studied in 121 patients
(100 men, 21 women) with primary lung cancer that was also treated
with surgery, radiotherapy, and/or chemotherapy. The PSK (3.0 g/day x
3 days, po) was administered at the same time as other initial
therapies. Chemotherapeutic agents included bleomycin, mitomycin C, 5-
fluorouracil, and urokinase. With respect to immunotherapy, the PSK
was administered alone to 37 patients, PSK + picibanil (OK-432) were
administered to 20, and no immunotherapy was administered to 64.
Among the patients with Stage III lung cancer, 12-mo survival rates
were significantly higher, and 50% survival period was 2x higher, in
the patients given PSK + OK-432 than in those given no immunotherapy.
Among the patients with Stage IV lung cancer, 50% survival periods
and crude survival rates were better in patients given immunotherapy
than in those not given immunotherapy, but significant differences
were not observed due to severity of the disease and incomplete
radiotherapy in the patients not given immunotherapy. Similar results
were observed between the patients given immunotherapy and those not
given immunotherapy when the tumors were analyzed according to
histological types, but the differences were decreased mo 20 after
treatment. (27 Refs)

Using in vitro clonal culture assays, we investigated the effects of
PSK, a protein-bound polysaccharide derived from the cultured
mycelium of CM101, Coriolus versicolor (Fr.) Quel in Basidiomycetes,
on human hemopoietic progenitors. PSK alone did not stimulate colony
formation by human bone marrow progenitors. Although 1-100
micrograms/ml of PSK had no effects on colony formation stimulated by
erythropoietin and medium conditioned by phytohemagglutinin-
stimulated leukocytes, more than 1 mg/ml of PSK inhibited all types
of colony formation. In contrast, medium conditioned by PSK-
stimulated leukocytes significantly stimulated formation of various
types of colonies including erythroid bursts, granulocyte and/or
macrophage colonies, eosinophil colonies, megakaryocyte colonies and
mixed hemopoietic colonies. It is speculated that administration of
the optimal dose of PSK can reduce the hematological suppression of
antitumor drugs.

*****NIPPON RINSHO. JAPANESE JOURNAL OF CLINICAL MEDICINE*****

(REFERENCE 35 OF 41)

Nomoto K
[POLYSACCHARIDE AND LIPOPOLYSACCHARIDE IMMUNOREGULATING MECHANISMS -
USE OF PSK AS AN EXAMPLE]

In: Nippon Rinsho (1981) 39(4):110-115 (Published in Japanese)

Characteristics of the mechanism and the effect of the polysaccharide
Kureha (PSK) were investigated as an example of immunopotentiation by
polysaccharides and lipopolysaccharides. Administration of PSK (50-
100 mg/kg ip or 1,000 mg/kg po, continuously) to sarcoma 180 or
Ehrlich tumor-bearing ICR mice resulted in disappearance of tumors
after transient growth of the tumor. Antitumor effects were also
observed for various homogenic strains of methylcholanthrene-induced
tumors. Administration of PSK in mice with sarcoma 180 tumors
increased splenocyte cytotoxicity. PSK had an inhibiting effect on
macrophage aggregation in normal mice, but had stimulating effect on
macrophage aggregation in tumor-bearing mice. Ip administration of
PSK in cancer bearing mice resulted in recovery of delayed-type foot
pad response to sheep RBC, and po administration resulted in a
slightly lower degree of recovery. Ip administration of PSK in
sarcoma 180 tumor-bearing mice with decreased production of
interferon due to poly I:C stimulation resulted in a certain degree
of recovery of interferon production. PSK was also observed to effect
(1) fluctuations in preventing infections due to cancer, (2) changes
in thymus function due to cancer, (3) inhibitory effects of cancerous
ascites, (4) fractions of immune-inhibiting factors from cancerous
abdominal ascites, and (5) mixes of accelerating factors and
inhibiting factors in cancerous ascites and serum. (5 Refs)

Although the antitumor effect of PSK can be increased by potentiating
the immune functions of PSK in tumor-bearing hosts, the mechanisms of
its action are not fully understood. In this study, we examined the
antitumor effect and CDDP combined effect of oral administration of
PSK on nude mice bearing a human ovarian cancer cell line (KF cells).
1. PSK was observed to have a significant antitumor effect in tumor-
bearing nude mice and subsequently to bring about an increase in the
survival rate and prolongation of the life span. 2. The antitumor
effect of CDDP was (but not significantly) enhanced by oral
administration of PSK and the prolongation of the life span of the
tumor-bearing nude mice was obtained. 3. Six weeks after tumor
inoculation, no significant natural killer (NK) cell activity in
spleen cells from untreated nude mice was observed. However, when PSK
(100 mg/kg but not 500 mg/kg) was given every other day, significant
NK activity was induced. 4. The serum immunosuppressive acid protein
(IAP) value in nude mice treated with PSK alone was significantly
higher than that in nude mice treated with a combination of PSK (100
mg/kg) and CDDP. These results suggest that CDDP prevents the
increase in serum IAP that occurs when PSK is used and that
consequently combinations of PSK and CDDP result in augmentation of
antitumor effects.

The effects of PSK, a protein-bound polysaccharide, on the survival
period and effector cell activity were examined using C57BL/6 mice
with melanoma B16. PSK prolonged the survival period of the mice with
tumors in a schedule- and dose-dependent manner. However, no life-
prolonging effect was observed when carrageenan-treated mice or
congenitally athymic mice were used as hosts. PSK enhanced the
cytostatic activity and interleukin-1-producing capacity of
peritoneal exudate plastic-adherent cells in C57BL/6 mice with
tumors. These findings suggested that PSK prolongs the survival
period of mice with B16 tumors through T-cell- and macrophage-
dependent mechanisms.

The effect of combination immunochemotherapy using interleukin-2 (IL-
2), PSK and cyclophosphamide (CY) was evaluated in a pulmonary
metastasis model in BDF1 mice. B-16 melanoma cells were inoculated
into a hind limb. On day 3 after inoculation, 20 mg/kg of CY was
administered intraperitoneally, and IL-2 (3.75 x 10(4) BRM
units/head) was injected into the tail vein on days 7, 8 and 9. PSK
(1,000 mg/kg) was administered orally every day from day 1 to day 10
using a stomach tube. This treatment cycle was repeated three times.
Using this combination therapy, the cytotoxicity of lymphokine-
activated killer cells and tumor-infiltrating lymphocytes was
enhanced. Pulmonary metastasis was remarkably suppressed and a
prolongation of survival was obtained compared with the nontreated
group and an IL-2+CY group. The effect was augmented by repeating the
therapy protocol. By analyzing the killer activity and surface
markers of tumor-infiltrating lymphocytes, it was recognized that
increased numbers of Lyt-2-positive T cells with augmented
cytotoxicity were obtained. This treatment modality should have
clinical significance.

*****PROCEEDINGS, ANNUAL MEETING OF THE AMERICAN SOCIETY OF CLINICAL*****

A randomized clinical trial was conducted by 46 participating
institutions from July 1985 to June 1987 in Chubu district to
evaluate the effect of biological response modifier PSK in curatively
resected advanced gastric cancer. After stratifying by serosal
invasion (T2, T3), 253 patients (pts) were randomly allocated into
the 5-fluorouracil (5-FU) and PSK group (Group P, n=124) and 5-FU
alone group (Group C, n=129). Bolus injections of mitomycin C (MMC) 6
mg/m2 were given to all pts on the first and seventh postoperative
days. At 2 wk after surgery, Group P began to alternately receive PSK
3 g/day for 4 wk and oral 5-FU 150 mg/day for 4 wk as 1 course: 10
courses were given. Group C received 5-FU alone for 4 wk with an
alternate rest interval for the same period. Pts characteristics
(age, sex, depth of tumor invasion, degree of lymph node metastasis)
were well balanced in the 2 groups. By June 30, 1992 the median
follow-up was 72 mo and all pts were followed up for at least 5 yr.
The 5-yr disease-free survival rate for Group P was 0.71 and was
significantly superior to that of Group C, which was 0.59 (p=0.047).
The 5-yr survival rate for Group P was 0.73 and for Group C 0.60 and
overall survival with MMC+5-FU+PSK was also significantly superior to
MMC+5-FU alone (p=0.044). In conclusion, addition of PSK to the
standard MMC+5-FU regimen results in a significantly superior
survival in pts who had undergone radical gastrectomy.

In order to evaluate the adjuvant immunochemotherapy with PSK in
curatively resected colorectal cancer, a randomized controlled study
by 35 institutions in Kanagawa Prefecture was conducted. From March
1985 to February 1987, 462 patients (pts) with colorectal cancer (any
TN1-3M0 or T4N0M0) were assigned to one of two different regimens. Of
these, 448 pts (97.0%) satisfied the eligibility criteria (colon, 249
cases; rectum, 199 cases). The control group received mitomycin C
(6.0 mg/m2) on the day and the day after the surgery, followed by 5-
FU (200 mg/day) given orally for over 6 mo. The PSK group received
PSK (3 g/day) po for over 3 yr, as well as mitomycin C and 5-FU as in
the control group. In February 1991, a follow-up study of these pts
was carried out to evaluate the survival rate for a minimum of 4 yr
after surgery. Both treatment groups were well matched, as they had
almost the same background factors. Disease-free rate (DFS) and
overall survival rate (OS) of the PSK group were significantly higher
than those of the control group (DFS: p=0.0250, OS: p=0.0296). Still
more, concerning colon cancers, in each subgroup with positive
preoperative CEA serum levels or Dukes’ C, the PSK group showed more
advantageous effects than those shown in the control group.

The protein-bound polysaccharide, PSK, has been used as a biological
response modifier in treating patients with cancer (Cancer Treat Rev
11:131-155 1984). Although the mechanism of its antitumor action is
not well understood, PSK enhances various immune responses in vivo as
well as in vitro. We have here examined the direct effect of PSK on
cytokine gene expression and production in human PBMC in vitro. As
determined by Northern blotting, PSK strongly induced gene expression
for interleukin 1 alpha, 1 beta, 6, 8, tumor necrosis factor alpha
and monocyte chemotactic and activating factor, but not for
interleukin 2 and lymphotoxin. Expression of mRNA occurs in 1-6 hr
using concentrations of 5-400 ug/ml of PSK. Furthermore, the
production of these cytokines in response to PSK can be detected by
ELISA or RIA. We conclude that these cytokines may mediate the
immunoenhancing action of PSK in vivo.